جمعیت میکروبی

Every year, a significant amount of saffron petals remains as a by-product after harvesting and separating the thread-like parts of the flower (stigmas). The saffron stigma constitutes only 7.4% of the flower's weight and the remaining 92.6% is unused. This plant residue (petals) is a valuable source of plant bioactive compounds (phytobiotics), which based on previous studies, has useful effects on rumen fermentation, digestion and diet efficiency. However, there is no specific information about the effect of this by-product on ruminal microbial populations, enzymatic activity, antioxidant health, as well as the mechanism of effectiveness. In the present study, it was hypothesized that the use of low levels of saffron petals in the diet (as a natural additive) could improve microorganism populations, hydrolytic enzymes and antioxidant health of the rumen. Therefore, this research was carried out to investigate the mechanism of the positive effects of saffron petals on the energy and nitrogen metabolism and antioxidant health of the sheep rumen using the in vitro method.  Experimental treatments included a diet without saffron petals (control) and diets containing 1, 2, and 3% of saffron petals (based on dry matter). The 24 and 72-h gas production tests were performed in 2 series (runs; in different weeks) and 3 replicates in each run (i.e., 6 observations per treatment at each incubation time). The gas production from the samples incubated in the 100-mL glass syringes was recorded. Then, the protozoa (using a hemocytometer and light microscope), cellulolytic and proteolytic bacteria (using liquid medium and Hungate tubes), hydrolytic enzymes (via chemical methods and photometry), methane (by injecting NaOH solution to absorb CO2) and antioxidant capacity (via ferric reducing antioxidant power assay) were measured. Truly degraded substrate was determined by boiling fermentation residues in the neutral detergent solution and weighing, ammonia-N by phenol-hypochlorite method, and the volatile fatty acids (VFA) using gas chromatography. Microbial biomass production, digestibility, metabolizable energy and partitioning factor were estimated using the equations. Data were analyzed using the Proc GLM of SAS 9.1 in a completely randomized design (6 observations per treatment).  The inclusion of different levels of saffron petals in the diet decreased the in vitro ruminal protozoa population (P<0.05), due to its bioactive components, which damage the structure and function of the protozoa membrane, deactivate protozoa enzymes or deprive protozoa of the substrate and metal ions needed for their metabolism. Moreover, saffron petals increased the cellulolytic bacteria numbers and microbial biomass production (P<0.05). This was due to the reduction of protozoa, which leads to the reduction of the bacteria predation and thus improves the growth and population of the cellulolytics. The ruminal fibrolytic enzymes and amylase activity decreased with the use of saffron petals in the diet (P<0.05), because of the higher cellulolytic bacteria and microbial biomass, i.e., higher bacteria activity. These improvements resulted in more (P<0.05) diet digestibility, metabolizable energy, total VFA and truly degraded substrate in the saffron petals-containing groups. The inclusion of saffron petals in the diet resulted in decreasing in vitro ruminal methane release, ammonia-N production and acetate-to-propionate ratio (P<0.05). These changes were due to the decreased protozoa numbers leading to less hydrogen supply for methanogens and higher hydrogen shift toward propionate, as well as less deamination process and ruminal nitrogen recycling. Another reason was the increase of cellulolytic bacteria that consume ammonia as their main nitrogen source. Antioxidant capacity increased with the use of saffron petals in the diet (P<0.05), due to the bioactive compounds and antioxidants (such as flavonoids) present in this plant residue. The maximum truly degraded substrate was observed in the diet containing 3% of saffron petals. The lowest methane, protozoa and ammonia were in diets containing 2 and 3% of saffron petals. Moreover, adding 2 and 3% of saffron petals caused the highest antioxidant power.  The results showed that the positive effect of saffron petals on the ruminal metabolism and antioxidative health of sheep, in vitro, was due to the beneficial changes that occurred in microbial populations (increase of cellulolytic bacteria and decrease of protozoa), hydrolytic enzymes (fibrolytic enzymes and amylase) and its antioxidants. Therefore, low levels (up to 3% of diet) of saffron petals can be used as a natural phytobiotic additive to improve rumen fermentation and reduce loss of energy and nitrogen resources, although it is better to confirm the results in vivo

Gerbera is one of the important cut flowers in the floriculture industry, but it is sensitive to early wilting and neck bending which reduce its postharvest vase life. In cut flowers, water deficits are created when transpiration is more than water absorption. Therefore, petal wilting and neck bending increase in these flowers. These conditions are mainly due to occlusion of the vascular bundle, which can occur in different ways, such as the activity of pathogenic bacteria and other microorganisms in vascular bundle. In recent years, due to the adverse effects of chemical antimicrobial compounds on human health and the environment, many studies have been conducted to find replacement materials to maintain the quality and vase life of cut flowers in postharvest. Therefore, in this study, the effect of different concentrations of harmel aqueous-alcoholic extract (Peganum harmala L.) on bacterial population and vas life of ‘Stanza’ and ‘Pink Elegance’ cultivars of Gerbera cut flower were studied.

The effect of concentrations 0, 0.25, 0.5, 0.75 and 1% of the aqueous-alcoholic extract of Harmel plant was studied in a factorial experiment based on completely randomized design with four replications. At harvest time, 3, 6 and 9 days after harvest (at 20 °C and 70% relative humidity), the effect of treatments on the bacterial population of the vase solution and end stem, vase life and some characteristics of ‘Stanza’and ‘Pink Elegance’ Gerbera cut flowers were studied.

The results showed that the inhibitory effect of harmal extracts on gram-positive bacteria was higher than gram-negative bacteria. Also,‘Stanza’cultivar had better quality and longer vase life than ‘Pink Elegance’ cultivar. By increasing the vase life of flowers, the quality of these flowers decreased. In the first place, however, concentrations of 0.25% and then 0.5% of the harmal extract performed better than other treatments in various aspects: first, they reduced the bacterial solution, stem end, and electrolyte leakagein stem and petals; second, they preserved quality (discolored of vase solution, discolored of petals and stem), relative fresh weight, stem diameter, totalsolublesolids, catalase activity and phenylalanine ammonia lyase activity; and finally, they increased vase life of gerbera flowers in both cultivars. Concentrations of 0.75% and 1% increased allelopathic substances in cut flower. While these treatments decreased the bacterial population in vase solution and stem end, they did not have a significant effect on the quality and vase life of gerbera cut flowers.

The results of this study showed that the different concentrations of harmal extract significantly reduced the growth of microbial agents, including the bacterial population, but by increasing the concentration of the harmal extract, the allelopathic effects of this plant extract on gerbera cut flowers were harmful and did not affect their vase life and quality. Therefore, the concentration of 0.25% then 0.5% reduced the bacterial populations in vase solution and stem end of cut flowers and preserved the quality and vase life of ‘Stanza’ and ‘Pink Elegance’ cultivars. Therefore, the use of low concentrations of the harmel aqueous-alcoholic extract is recommended to reduce the microbial population of the vase solution and maintain the quality and vase life of the gerbera cut flowers.

Gerbera is one of the most important cut flowers in floriculture industry and has high economic value. One of the main problems in gerbera export is postharvest losses and short vase life due to the water relations disruption by the increasing of microbial population in preservative solution. During last decades awareness increased among peoples regarding side effect of chemicals used in agriculture and several research has been conducted to find alternative methods or materials to preserve product quality or prolong vase life.
In this study the effect of essential oils of ajowan, lavender, and eucalyptus with two concentrations (15 and 30 l L-1 L) and silver nanoparticles with two concentrations (40 and 80 l L-1 L) on vase solution uptake, membrane stability index of stem and petals, petals wilting percentage, microbial population at the end of stem and vase life of cut gerbera cv. Pink Power were investigated. A factorial experiment (the first factor was treatments and the second factor was sampling time) was conducted in a completely randomized design (CRD) with three replications and four flowers in each replication.
The different treatments of plant essential oils and silver nanoparticles had not sensible effect on some of traits such as relative fresh weights of cut flowers, the changes of stem diameter in the below of flower head and end of stem and petals ion leakage. Conversely, some of traits such as the vase solution uptake, membrane stability index, stem ion leakage, microbial population at the stem end, petal wilting percentage and vase life significant affected. Essential oil of ajowan (15 l L-1 L) increased vase solution uptake and reduced microbial population, ion leakage petal, wilting percentage and, consequently, increased the vase life of gerbera. The highest vase life (11 days) was related to 15 l L-1 L ajowan treatment, although there was no significant difference with compared to silver nanoparticles
In general, essential oil of ajowan and silver nanoparticles used in this study were able to improve the vase life of gerbera cut flowers. But, due the superiority of some measured traits of gerbera cut flowers treated with essential oil of ajowan compared to silver nanoparticles, and harmful environmental effects of silver nanoparticles, can be recommended the ajowan essential oil with 15 l L-1L concentration be used for increasing the vase life of gerbera. However, since gerbera plants are highly heterozygous, further researches on other cultivars with different concentrations may be suggested.